There is an increasing need in the industry, for example in the food, pharmaceutical or cosmetics industry, for protection of active agents from the medium that surrounds said active agents in particular to achieve a better conservation of said active agents.
One of the main issues of encapsulation is to be able to protect drugs from external medium but also to allow the right release or the right access to this drug when needed. This access is very often possible through a quick or controlled release in the medium, due to chosen properties of the encapsulating agent.
This dual aim of protection and release becomes more complex as soon as exchanges between drugs and medium need to be kept out of direct interactions in-between drug and external medium. S. K. Tam and al. have shown (in Vandamme et al Microencapsulation; Tec & Doc; 2007; Chapter 11) these issues when the microencapsulation aims to allow therapeutic effects through useful component exchanges, components which are able to cross the microencapsulation barriers while preserving drugs from being in direct contact with other potentially damaging components, if they had entered the microcapsule.
In case of oxidizable drugs, the issue is to be able to get microcapsules which are able to protect these drugs from oxidation, and to protect the external medium from component issued from oxidation of said drugs.
Different kind of encapsulating agents can target this type of protection, but polysaccharides are the most often used. They are mainly used under bead forms containing solutions and cross-linked in salt or cations solutions. Such beads are then stored in wet forms as suspensions particles in solutions.
Chen and al. Journal of Controlled Release 2004, 96, 285-300 reported that such beads of polysaccharides can protect bioactive molecules from harsh acidic conditions such as stomach environment. But no works seem to have been made on the use of such a protection of the external medium from oxidizable agents which could decompose media components.
Moreover, the use of such polysaccharides is mainly achieved with cross-linking through dropping of aqueous solutions containing said polysaccharides into aqueous solutions containing salts.
However, the obtained, beads suffer several drawbacks: they are mainly stored in aqueous solution, rendering their handling difficult, their production and their transportation expensive. In addition, said beads cannot be used directly in powder preparation, in particular food powder compositions, or in tablets, in particular for pharmaceutical uses.
No studies have been made on powder microcapsules allowing dry forms of drug protections through process avoiding aqueous solution to create the insoluble external protection of the microcapsule.